I swear that the most dangerous driving I see is when a car has been stuck behind a slow moving vehicle (going way below the limit) for ages and can't overtake because of oncoming traffic/white line/can't see round corner/other cars in the train not getting on with their overtake etc. Then the frustrated car finally spies half an opportunity to overtake and even though it's a bit dangerous they take it as they've got so fed up of going slow.
Similarly when stuck behind a slow moving vehicle in corners/uphill, they're then looking for an opportunity to overtake... but when the opportunity finally arrives, we're now on straight/flat road and the slow moving vehicle is now doing a decent pace (but will be slow again at the next corner/uphill), so to get past the slow car, who has now sped up, the frustrated car has to overtake at warp10 silly speed.
In both cases if the slow vehicle had been doing a decent pace or not slowing down ridiculously for corners/uphill, the vehicle behind wouldn't get frustrated and coaxed into taking a dangerous overtake at half an opportunity.